Method for treating a bulk material with a fluid

ABSTRACT

PCT No. PCT/SE78/00092 Sec. 371 Date Aug. 10, 1979 Sec. 102(e) Date Aug. 10, 1979 PCT Filed Dec. 11, 1978 PCT Pub. No. WO79/00375 PCT Pub. Date June 28, 1979 
     A bulk material is treated in a drum rotating in a bulk of the bulk material to be treated. The drum (16, 68) is provided with feeding-in openings (28, 70) in the cylindrical face of the drum. The bulk material tumbles around in the drum and is conveyed towards a discharge part in one end of the drum by means of a worm conveyor in the drum rotating in opposite direction to the drum. A treatment fluid is introduced into the drum through apertures (11a, 85) in the shaft of the worm conveyor. After the fluid has treated the bulk material in the drum it is led away through the same openings (28, 70) as those through which the bulk material is continuously being fed into the drum. Further the fluid advances up into the bulk of bulk material which therethrough also is treated before the material is fed into the drum. The method and the apparatus is particularly intended for treating pulp wood chips, e.g. for presteaming chips and for washing chips. In the former case one or more drums are provided horizontally in a container for the chip material, closely above the bottom of the container. In the latter case the drum is provided slopingly for conveying the chip material up through the container at the same time as the chip material is being washed.

FIELD OF THE INVENTION

The present invention relates to a method of treating a bulk materialwith a gaseous, vaporous, or liquid fluid. For example the inventionrelates to a method of presteaming or other treatments of chopped woodchips for cellulose production by means of a fluid in the form of watersteam. The invention also relates to an apparatus for carrying out themethod.

Another example of how the invention may be applied is the treatment ofchopped wood pulp chips in order to thaw snow and ice which frequentlyexist in northern countries in bulks of chips which are stacked outdoorsand which often cause problems in the initial part of the chip treatmentprior to digesting. Another example of the applicability of theinvention is for drying grain or other particulate materials wherein thetreatment fluid normally is hot air. Another area where the principlesof the invention may be applied is for effecting chemical reactionsbetween a fluid in the form of a reactive gas, vapour or liquid, and forexample a mineral concentrate. A further example of the applicability ofthe invention is for washing solid particles or objects, wherein thefluid may be a liquid washing or solution agent. This application of theinvention may be used i.a. for washing wood chips with water in order toremove gravel, sand and similar heavy contaminations.

BACKGROUND ART

The Swedish Pat. No. 221 188 discloses a method and an apparatus forcleaning chopped cellulose chip material from accompanying foreignparticles. The apparatus comprises a dewatering device equipped with aworm conveyor which suitably is inclined and surrounded by a perforatedwall. During the course of the chip being fed upwards in the wormconveyor finer impurities such as sand particles are separated. Theseparated particles pass through the perforated wall together with thewater and are fed through a conduit to a sand trap. The perforations ofthe partition wall are adapted to the size of the impurities which shallbe removed, which means that the size of the perforations is chosen suchthat the chips essentially cannot pass therethrough but substantiallyproceed upwards and are delivered to an outlet. Due to the fact that thechip material is fed in at one end and discharged at the other endwithout being able to pass through the perforated wall the bulk of chipmaterial in the helicoidal passage-way through the worm conveyor will becomparatively compact. Nor does the worm to any significant extenttumble around the bulk of chips in the conveyor, and therefore thewashing of the chips during the transportation of same through theconveyor will not be highly efficient.

The Swedish Pat. No. 171 489 discloses an apparatus for drying malt orother lump material. The apparatus comprises a rotatable cylindric drumthrough which the material to be dried is brought to pass from one gableto the other. The rotating drum is surrounded by a fixed drum so that asectioned annular space is formed between the drums. Air for drying thematerial in the inner drum is fed in and led away through thesemi-circular channels in the annular space. Further there is provided acentral worm in the inner drum for conveying the material. The apparatushas i.a. the limitation that the outer drum excludes the possibility oftreating material also outside the rotating drum simultaneous with thetreatment of material inside the drum. The apparatus also is based onthe principle that the apertures in the perforated drum are so smallthat only the treatment fluid, in this case air, can pass through theapertures but not the material to be treated. The latter thereforecannot pass in or out through the cylindrical wall of the drum duringthe treatment which renders any homogenous feeding-in of new materialalong the perforated length of the drum impossible at the same time asfinished material is discharged through the end of the drum.

In certain respects similar but in still higher degree closed systemsare shown in the Norwegian Pat. No. 27 159 and the Danish Pat. No. 15876.

Further there is disclosed in the Swedish Pat. No. 398 633 an apparatusfor discharging vessels. The apparatus comprises a vertical fixednon-perforated drum with a central worm conveyor. The shaft of the wormconveyor is perforated so that compressed air or other fluid can beinjected through the shaft into the helicoidal passage way of theconveyor which facilitates the transportation through the drum. But dueto the fact that the drum is fixed it is nor by means of this apparatusas in the apparatus according to the Swedish Pat. No. 221 188 achievedany tumbling action, and as the apparatus moreover is totally encased,i.e. non-perforated, there is nor achieved any interaction with oraffect upon the environment of the drum.

DESCRIPTION OF THE INVENTION

The above mentioned drawbacks and limitations of previous methods andapparatuses may be eliminated through the invention therein that thebulk material is treated in a drum surrounded by a bulk of the materialto be treated, that the bulk material is fed in into the drum throughopenings in the cylindrical face of the drum, that said fluid isintroduced into the helicoidal space between a worm conveyor for saidbulk material inside the drum and the drum encasing the worm conveyor,said worm conveyor being rotated in a direction opposite to that of thedrum making the treatment of the bulk material in the drum moreefficient due to the obtained loose distribution of the bulk material inthe drum and due to the fact that the bulk material tumbles around inthe drums, and that at least a portion of the fluid is caused to leavethe drum through the same openings in the cylindrical face of the drumas those through which the bulk material is being fed in.

When the invention is utilized for presteaming pulp wood chips the wormconveyor with the surrounding hole-provided drum is mounted in a chipbin, suitably closely above the bottom of the chip bin in order todischarge the chip material from the bin in the lower portion of thebin. After the steam has been contacted with the bulk of chips whichpresently exists in the drum, the steam proceeds via the openings in thedrum up into the bulk of chips in the bin so that also this bulk ofchips successively is presteamed which is made possible through the factthat the drum is located in and is surrounded by the chip material inthe chip bin. The chip material in other words will meet the steam asthe steam successively is advancing downwards in the bin wherethroughthe steam is very efficiently utilized. The good presteaming effect alsois stimulated by the fact that the chip material in the bin is keptmoving by the rotating hole-provided drum in the bottom section of thebin. Suitably also a corresponding worm conveyor with surrounding drumis provided in the upper part of the bin for feeding in chip materialinto the bin. In that case however, the principles of the invention areutilized only partially.

Also in the case when it is aimed at using the invention e.g. forwashing wood chips the worm conveyor is provided with the surroundingdrum in the bulk of bulk material, suitably closely over the bottom ofthe vessel--the washing tub--which then is made sloping as the"tube-feeder". The washing water is suitably fed in counter-currentwiseinto the drum and therefrom into the washing tub, while the chipmaterial is discharged up from the vessel through the drum.

In order to introduce the treatment fluid in an efficient manner intothe helicoidal passage of the worm it is suitable for that purpose touse the shaft of the worm conveyor which hence is perforated. Theapertures in the shaft of the worm conveyor are suitably so small thatpulp material to be treated essentially shall not be able to passthrough while the number of perforations on the other hand is sufficientto obtain the desired flow of the fluid to be injected. This means thatthe apertures in the shaft of the worm conveyor have a size of a quitedifferent order than the openings in the cylindrical face of the drumwhich openings shall be so large that the bulk material withoutdifficulty may pass through. The principle thus is that the fluid isurged into the space between the shaft of the worm conveyor and thecylindrical face of the drum via the apertures in the shaft of the wormconveyor, that the fluid is caused to contact the bulk material in thedrum, and that the fluid thereafter is caused to leave the drum throughthe openings in the cylindrical face of the drum, said fluid thenmeeting the pulp material which is continuously fed in through saidopenings.

The advantages and principles of the invention will be apparent more indetail from the following description of two preferred embodiments.

BRIEF DESCRIPTION OF DRAWINGS

In the following description of two preferred embodiments it will bereferred to the accompanying drawings, in which

FIG. 1 is a side view of a plant for presteaming wood pulp chips;

FIG. 2 shows the same plant from the left in FIG. 1; and

FIG. 3 is a side view of a plant for washing wood pulp chips.

In the drawings only such details are shown which are important for theunderstanding of the invention, while other details have been omitted inorder to make the essential parts more clear.

DESCRIPTION OF PREFERRED EMBODIMENTS

Referring to FIGS. 1 and 2 a container for chopped wood chips forcellulose production has been generally designated 1. The container 1has two length sides 2 and two gables or short sides 3. The sides 2, 3and roof 4 consist of sheets connected by vertical beams 5 andhorizontal beams 6. The front side 2 has been partly cut up in FIG. 1 todemonstrate the bulk of wood pulp chips 7 in the container. The bottomportion has the shape of tub or trough 8, which extends past the twoshort sides 5 of the container. The extending portions have beendesignated 8' and 8". In a longitudinal opening in the roof sheet 4there is provided a vaulted top structure 9.

In the trough 8, just over the bottom, there are horizontally mountedtwo parallel worm conveyors 10. Each of these worm conveyors consists ofa shaft 11 and a screw blade 12 attached thereto. The shafts are mountedin one end in bearings 13 and are driven by a joint hydraulic motor 15via a chain gearing 14 which is not disclosed in detail in the drawings.

Each worm conveyor 10 is surrounded by a concentric drum 16 extendingalong the whole length of the worm conveyor and projecting past itsends. That end of the drum 16 which is turned to the shaft bearing 13 ismounted on the shaft 11 by a bearing 17. The opposite end of the drum 16is mounted on the shaft 11 by a support bearing 18, the supports beingdesigned like propeller blades attached to the drum 16. The propellerblades of the support bearing 18 are by welding joined to a shaftportion 21 having the form of a sleeve mounted in a bearing 19 in apartition wall 20 and in a bearing 22 in an end wall 23. Between thewalls 20 and 23 the sleeve 21 is provided with four openings distributedaround the circumference of the sleeve. The chamber between the walls 20and 23 has been designated 25. The sleeve 21 and hence the supportbearing 18 and the drum 16 are provided to be rotated in the oppositedirection to the shaft 11 by means of a hydraulic motor 26 via a chaingear 27. Both the drums 16 are analogously designed, i.e. provided withsupport bearings 18, sleeves 21 etc and are driven by the jointhydraulic motor 26 via the chain gear 27. In each drum there are made anumber of openings in the form of oval holes 28 which are distributedover the whole length of the cylindrical face of drum between thesupport bearing 18 and a line parallel with the further (referring tothe support bearing 18) short side 3 of the container 1, or possibly alittle bit further. The holes 28 are also distributed around theperiphery of the drum 16 so that in each section of the drums there isat least one hole 28. Suitably the holes 28 are distributed helicallyaround the drums. Further the holes 28 are so big that the bulk materialto be treated, i.e. the chip material 7, readily may pass through theholes. The size of the holes 28 in the cylindrical face of the drum 16thus is of a quite different order than the small apertures 11a in theshaft 11.

In the further end of the extension 8' of the trough 8 each drum 16 isprovided with six larger substantially rectangular openings 29 above achip discharge conduit 30. Further, according to the invention, aconduit 31 for feeding steam is connected to the chamber 25 in theextension 8" in the left hand part of trough, and a conduit 32 fordrawing off of surplus steam is connected to the extension 8' in theright hand part of the trough.

In the top structure 9 there is provided one single worm conveyor 35having a shaft 36 and a screw blade 37 attached thereto. In the manneras has been described with reference to the equipment in the trough 8,the worm conveyor 35 in the top structure 9 is surrounded by a drum 38having holes along its whole length between two partition walls 40 and41. The former front partition wall 40 is provided in that end of thedrum 38 which is turned to that end where the chips are fed in, whilethe latter, the rear partition wall 41 is provided at a distance fromthe further gable 42 of the top structure 9. Between the front partitionwall 40 and the drum 9 there is an annular gap through which gases canpass, while the rear partition wall 41 is tightly engaged to the surfaceof the drum 38.

In the chip feeding-in end the top structure 9 has an extension 9'provided with a connection 43 for feeding chips to a chamber 52 definedby said extension. In the discharge end, in a discharge chamber 51between the partition wall 41 and the gable 42, the drum 38 is providedwith a number of larger chip discharge openings 44. The shaft 36 ismounted in end bearings 45 and 46, and is driven by an hydraulic motor47. The drum 38 is mounted in an end bearing 48 and in a support bearingsaid type which has been previously described and which is provided withsupports in the form of propeller blades. The drum 38 is driven in adirection opposite that of the worm conveyor 35 by means of an hydraulicmotor 50. A connection for supplying steam into the chamber 51 in thechip charging end has been designated 53.

The described apparatus operates in the following manner. Chip materialis fed into the entry chamber 52 through the connection 43 from a stackwhich as a rule is located in the open. The motor 47 rotates the wormconveyor 35 in such a direction that the chip material is fed throughthe support bearing 49 into the drum 38 and progressively towards thedischarge openings 44. Through the discharge openings 44 the chipmaterial falls down into the container 1. Part of it also falls downinto container 1 through the openings 39 in the cylindrical face of thedrum 38 which is facilitated by the fact that the drum at the same timeis rotated in the opposite direction to that of the worm conveyor 35.

Steam is supplied to the chip discharge chamber 51 through theconnection 53. From the chamber 51 steam is pressed--sucked--in throughthe chip discharge openings 44 and progressively into the drum 38. Partof the steam goes out through the openings 39 and into the space betweenthe drum and the casing which forms the roof and wall of the topstructure 9 and therefrom through the gap between the partition wall 40and the drum 38 into the chip entry chamber 52. The main portion of thesteam is, however, pressed--sucked--helically forwards between theinside of the drum 38 and the screw blade 37 and hence meets the chipmaterial which is continuously fed into the drum. Part of the steam iscondensed upon the chips and/or attributes in melting snow and ice whichin winter time as a rule accompany the pulp wood chip material which isbeing fed in. Surplus steam pass through the support bearing 49 into thechip entry chamber 52 wherefrom the steam is sucked out through conduit54.

The equipment in the bottom portion of the apparatus operates in thefollowing manner. The bulk 7 of chip material is successively fedthrough the openings 28 in the cylindrical faces of the drums 16 intothe two rotating drums 16 in which the chip material forms a loose bodyof chip material tumbling around in the drums at the same time as thechip material is forced towards the discharge openings by means of theworm conveyor 10. The drums 16 therefore can be said to be diggingaround in the bulk 7 of chip material which homogeneously is fed intothe drums over substantially the entire bottom area of the container 1.At the same time the rotating drums 16 give rise to a certain movementin the entire bulk 7. Steam is fed into the chamber 25 through the steamconnection 31. From the chamber 25 steam is pressed--sucked--into eachsleeve 21 through the openings 24 and from the sleeves 21 into thetubular shaft 11 and therefrom into the respective drum 16 through theapertures 11a. In the drums 16 the steam meets the loose body of chipmaterial which is tumbling around and which then is efficientlypresteamed by the steam. The efficient stirring and the loose body ofchip material is then of essential importance for a good presteamingresult. Surplus steam is led away through conduit 32 while the main partis utilized for presteaming wood chip material. This is performed in thefirst place in the drums 16 where the steam is caused to contact thebulk of chip material which continuously is fed in through the openings28 in the cylinrical faces of the drums but also in the container 1through the fact that the main part of the steam successively will passout through the openings 28 in the drums, where the steam will meet thechip material which is being fed in through the same openings, whereuponthe steam will advance up through the bulk 7 of chip material. Thepresteaming action can be stimulated by suitably adapting the pressuresin the conduits 31, 32 and 53, 54 to each other. As the chip material 7is successively fed down in the container 1 it will thus meet warmer andmore " virgin" steam wherethrough the presteaming result is made moreefficient and the steam will be utilized in a more optimal way. In orderfurther to improve the efficiency of the treatment, more particularly tomake the stirring of the bulk of chip material in the container and the"digging function" of the drum more efficient the drums 16 may bemovable sideways and/or in the vertical direction in the container 1.

Referring now to FIG. 3 a vessel or tub for washing of wood chips isgenerally designated 60. The bulk of wood chips intended to be washed isdesignated 61. The washing vessel 60 is filled with water up to a level62 which is determined by a spillway 84. The bottom 63 of the vessel isdished and is inclined upwards. Further the bottom 63 is perforated byholes 64 for the transfer of small stones, sand and other heavypollutants to a bottom pocket 65. From the bottom pocket the heavypollutants can be removed through a conduit 66. The perforated floorplate or strainer 63 can be cleansed by back-washing with water throughconduit 66.

A cylindrical chip conveying tube 67 extends slopingly up from thevessel 60. In the tube 67, just above the perforated bottom 63, there isprovided a drum 68 with a worm conveyor 69. The drum 68 is provided withpassage openings in the form of oval holes 70 in the region of thevessel 60 but preferably not in the region of the tube 67. The drum 68is provided to be rotated by a motor 71 via a sleeve shaped shaftportion 72, while the worm conveyor 69 is provided to be rotated in theopposite direction by a motor 73. Suitably the drum 68 is provided withexternal flanges, tappets, or other projecting members which may movechips in the bulk of chips 61 forward at the rotation of the drum. Dueto the rotation of the drum 68 and the worm conveyor 69 chips are fedinto the drum through the holes 70 and are transported up from thevessel 60 through the tube 67 and out from the tube through dischargeopenings 74 in the upper end of the drum 68. A discharge conduit 75 forwashed chips is provided below said discharge openings 74. Moreparticularly said openings 74 are provided between a support bearing 76of the type above described and an end bearing 77.

The sleeve shaped shaft portion 72 extends through the end bearing 77 ofthe drum and is fastened by welding to the support bearing 76. Furtherthe sleeve 72 extends through an intake chamber 78 for fresh washingwater and through a partition wall 79. A connection conduit for freshwashing water to chamber 78 has been designated 80. In the region of theintake chamber 78 the sleeve 72 is provided with a number of intakeopenings 81 for fresh washing water whch is fed into chamber 78 throughconduit 80. From chamber 78 the washing water is brought into the sleeve72 through the openings 81, and from the sleeve 72 it is thereafterbrought into the drum 68 via a narrow space 82 between the sleeve 72 andthe shaft 83 of the worm conveyor. Fresh washing water consequentycontinuously meets the chips which continuously are transported upwardsin the drum 68 from the washing vessel 60. Used washing water is drainedoff through the spillway 84 in the upper part of the tube 67, whereafterthe water can be recirculated and reintaken into the chamber 78 throughconduit 80, possibly after straining or other purification. The majorityof heavy particles existing in the bulk of chips are removed already inthe vessel 60 when the chips are agitated by the drum 68 and sink downto the bottom 63 and are collected in the pocket 65. Such heavyparticles which, however, are introduced into the drum 68 are forceddownwards through the drum by means of the washing water which is takenin in the upper part of the drum in the manner above described and aredischarged from the drum together with the washing water through theopenings 70 in the lower part of the drum. A very efficient washingtakes place in the drum due to the fact that the quantity of chips inthe drum is not compact but loose and is agitated, and to the fact thatfresh washing water is continuously supplied countercurrentwise.

I claim:
 1. Method of treating a bulk of bulk material with a fluid, said method comprising treating the bulk material in a drum, which is surrounded by a bulk of the material to be treated, said drum including a plurality of openings distributed over the cylindrical face of the drum and a worm conveyor for said bulk material inside said drum, by feeding the bulk material into said drum through said openings while rotating said drum around its axis in said bulk of bulk material, introducing said fluid into the helicoidal space between said drum and said worm conveyor, rotating said worm conveyor at least at times in a direction opposite to that of the drum, to make the treatment of the bulk material more efficient due to the obtained loose packing of the bulk material in the drum and due to the fact that the bulk material is tumbled around, causing at least the main portion of the fluid to leave said drum through the same openings in the cylindrical face of the drum as those through which the bulk material is being fed in, and also treating material in the bulk material above the drum with the fluid passing through said openings in the drum.
 2. Method according to claim 1, wherein the bulk of said bulk material surrounding said drum is located within a container, and said bulk of said bulk material is only discharged from said container by way of the space between said worm conveyor and said drum.
 3. Method according to any of claim 1 or claim 2 wherein said fluid is introduced into the drum through apertures in the worm conveyor shaft and passes through the space between the worm conveyor and the cylindrical face of the drum in order to treat bulk material tumbling around in said space before the fluid passes through the openings in the cylindrical face of the drum, said fluid then treating the bulk material which continuously is fed into the drum along the entire part of the length of the drum which is provided with openings.
 4. Method according to claim 1 or claim 2 wherein the bulk material consists of wood chips and the fluid consists of steam for presteaming the chips.
 5. Method according to claim 1 or claim 2 wherein the treatment is performed while the bulk material is transported upwardly by means of a sloping worm conveyor and the rotating drum enclosing the worm conveyor, and said fluid is a liquid said fluid is fed into the drum in the upper part of the drum and discharged from the drum through passage openings in the lower part of the drum. 